Ben & Jerry’s have an independent board of directors and a good relationship with parent company Unilever, but wasn't all plain sailing. Photograph: James Morgan/Rex

There has been concern for a number of years about the fate of socially responsible businesses that get swallowed up by larger mainstream corporations. Do they lose their independence and radical edge, or do they help drive innovative thinking within the parent company?

However, ice cream maker Ben & Jerry's, owned by Unilever, says that it is now showing that a more transparent path is possible with the announcement that it has joined the rapidly expanding socially responsible B Corporation movement in America.

The company is the first wholly owned subsidiary to be certified by the non-profit B Lab to show that it meets rigorous standards of social and environmental performance, accountability, and transparency.

Ben & Jerry's hopes its leadership will encourage other major corporations to give some measure of independence to their more progressive subsidiaries.

The company becomes the 635th business to join the movement, which is gaining critical mass in securing legislation to support its socially responsible business model. Eleven US states have already enacted laws supporting entrepreneurs and investors to build a more inclusive and sustainable economy, and a 12th is on the way.

The legislation is needed because US corporate law effectively obliges directors to prioritise shareholder interests above all else.

Chief executive Jostein Solheim tells the Guardian: "As a wholly owned subsidiary of Unilever, the B Corp certification may even be a bit sweeter. When Ben & Jerry's was acquired, many folks thought it would be a challenge for the company to keep its values.

"We're thrilled to join the movement. To undergo the process of certification, where every facet of our business is scrutinised to ensure that we're walking the talk, is rigorous but rewarding. It allows an experienced, holistic, values-led third party entity that B Lab is the chance to affirm that we remain true to our mission and look to accelerate our social impact."

Solheim adds: "We feel other businesses will learn and benefit from this. That position of being the first wholly owned subsidiary to become a certified B Corp is tremendous. The level of transparency and willingness to be open and honest is a testament to the relationship between Unilever and B&J's, which we continually work for. It really helps put Ben & Jerry's back into the pioneering realm, this time for other businesses who may find themselves in a similar setting."

Highlights show that 45% of the cost of goods sold go toward investing in and supporting small scale suppliers through the Caring Dairy program; its lowest paid hourly worker receives 46% above the living wage, and between half and three quarters of staff took part in an organised community programme in the last year.

Between 65%-80% of its staff are "satisfied" or "engaged" at work, and the highest paid individual earns between 16 and 20 times more than the lowest paid full time worker.

Only 4% of suppliers have third-party social or environmental company level certification, but this rises to 24% on the basis of materials or products purchased.

Sensitive information that could advantage competitors or prejudice litigation, is blacked out, such as net income and the percentage of under-represented managers.

In terms of overall performance, Ben & Jerry's scored 93% of available points for its governance structure, 55% for environment and 45% for community.

Does Solheim feel the knowledge the company gains will have an impact up the chain in Unilever?

"We operate in a manner of open communication and sharing," he says. "As both organisations continue to pursue linked prosperity values be it in sourcing, social justice or sustainability we'll learn and succeed together. I've already spent considerable time with the Unilever CEO Paul Polman to discuss why we're proud of this announcement."

Andrew Kassoy, who came up with the original B Corp idea five years ago with two course mates from Stanford University, said it was too early to predict what impact the certification may have on Unilever, but he is hopeful that "the B impact assessment, as a tool to engage Unilever's supply chain on sustainability and to measure the increasingly positive impact Unilever has on the world by leveraging its enormous buying power, would be one compelling opportunity."

With Ben & Jerry's joining soon after outdoor clothing and equipment company Patagonia, Kassoy is hopeful that other large companies will join the fold. "Anytime a company with a large following like Ben & Jerry's joins the movement, it's a big deal," he says. "We expect Ben & Jerry's to embrace B Corp as they've embraced fair trade and that will help invite tens of millions of new consumers to be the change by supporting a better way to do business."

Kassoy believes that soon others will follow. "Larger and publicly-traded companies will begin to join the B Corp movement – some as certified B Corps, and many more will use the B impact assessment as a tool to engage their supply chains," he says. "There are already more than 7,000 businesses using the assessment as a free and confidential management tool and we expect larger corporations to see this as a powerful way to leverage their purchasing power to engage their suppliers to measure what matters."

While Ben & Jerry's won the right to have an independent board of directors at the time of the Unilever acquisition more than a decade ago, the relationship has been through stormy times. In the past, the ice cream maker has accused its parent company of trampling on its values by trying to force it to follow Unilever's global policies at the expense of what it believes is right. Those tensions have dissipated since Polman took charge.

Jerry Greenfield told the Guardian recently that there has always been "a fascination with what the relationship is like between Unilever and Ben & Jerry's. Do we have the freedom and how things have changed under their ownership? When we were over here the last time to announce our commitment to 100% fair trade, we thought we were doing this great thing, but the questions were about isn't Unilever trotting you out to make it look good and would you had done this a lot quicker if it was not for Unilever?"

Greenfield recalls company founder Ben Cohen admitting to the press they would have done it earlier and "Unilever did not really like that. The difference now is that since Polman is so committed to this sustainability programme, he has managed to change the general feeling. Now there is not nearly the same level of distrust."

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